Chromosome 21

Last updated
Chromosome 21
Human male karyotpe high resolution - Chromosome 21 cropped.png
Human chromosome 21 pair after G-banding.
One is from the mother, one is from the father.
Human male karyotpe high resolution - Chromosome 21.png
Chromosome 21 pair
in human male karyogram.
Features
Length (bp)45,090,682 bp
(CHM13)
No. of genes 215 (CCDS) [1]
Type Autosome
Centromere position Acrocentric [2]
(12.0 Mbp [3] )
Complete gene lists
CCDS Gene list
HGNC Gene list
UniProt Gene list
NCBI Gene list
External map viewers
Ensembl Chromosome 21
Entrez Chromosome 21
NCBI Chromosome 21
UCSC Chromosome 21
Full DNA sequences
RefSeq NC_000021 (FASTA)
GenBank CM000683 (FASTA)

Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, [4] with 46.7 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. Most people have two copies of chromosome 21, while those with three copies of chromosome 21 (trisomy 21) have Down syndrome.

Contents

Researchers working on the Human Genome Project announced in May 2000 that they had determined the sequence of base pairs that make up this chromosome. [5] Chromosome 21 was the second human chromosome to be fully sequenced, after chromosome 22.

Genes

Number of genes

The following are some of the gene count estimates of human chromosome 21. Because researchers use different approaches to genome annotation, their predictions of the number of genes on each chromosome varies (for technical details, see gene prediction). Among various projects, the collaborative consensus coding sequence project (CCDS) takes an extremely conservative strategy. Thus CCDS's gene number prediction represents a lower bound on the total number of human protein-coding genes. [6]

Estimated by Protein-coding genes Non-coding RNA genes Pseudogenes SourceRelease date
CCDS 212 [1] 2025-01-15
HGNC 215190194 [7] 2025-01-15
Ensembl 221450184 [8] 2024-05-13
UniProt 244 [9] 2024-11-27
NCBI 254637246 [10] [11] [12] 2025-01-19

Gene list

The following is a partial list of genes on human chromosome 21. For complete list, see the link in the infobox at the top of the article.

In addition, the chromosome has many genes for keratin-associated protein, with symbols: KRTAP6-1, KRTAP6-2, KRTAP6-3, KRTAP7-1, KRTAP8-1, KRTAP10-1, KRTAP10-2, KRTAP10-3, KRTAP10-4, KRTAP10-5, KRTAP10-6, KRTAP10-7, KRTAP10-8, KRTAP10-9, KRTAP10-10, KRTAP10-11, KRTAP10-12, KRTAP11-1, KRTAP12-1, KRTAP12-1, KRTAP12-2, KRTAP12-3, KRTAP12-4, KRTAP13-1, KRTAP13-2, KRTAP13-3, KRTAP13-4, KRTAP15-1, KRTAP19-1, KRTAP19-2, KRTAP19-3, KRTAP19-4, KRTAP19-5, KRTAP19-6, KRTAP19-7, KRTAP19-8, KRTAP20-1, KRTAP20-2, KRTAP20-3, KRTAP20-4, KRTAP21-1, KRTAP21-2, KRTAP21-3, KRTAP22-1, KRTAP22-2, KRTAP23-1, KRTAP24-1, KRTAP25-1, KRTAP26-1, KRTAP27-1.

Diseases and disorders

The following diseases and disorders are some of those related to genes on chromosome 21:

Chromosomal conditions

A karyotype of somebody affected with Down syndrome, depicting the presence of a full additional copy of chromosome 21. The presence of this extra copy is also referred to as Trisomy 21. Trisomie 21 Genom-Schema.gif
A karyotype of somebody affected with Down syndrome, depicting the presence of a full additional copy of chromosome 21. The presence of this extra copy is also referred to as Trisomy 21.

The following conditions are caused by changes in the structure or number of copies of chromosome 21:

Cytogenetic band

G-banding ideograms of human chromosome 21
Human chromosome 21 ideogram vertical.svg
G-banding ideogram of human chromosome 21 in resolution 850 bphs. Band length in this diagram is proportional to base-pair length. This type of ideogram is generally used in genome browsers (e.g. Ensembl, UCSC Genome Browser).
Human chromosome 21 - 400 550 850 bphs.png
G-banding patterns of human chromosome 21 in three different resolutions (400, [15] 550 [16] and 850 [3] ). Band length in this diagram is based on the ideograms from ISCN (2013). [17] This type of ideogram represents actual relative band length observed under a microscope at the different moments during the mitotic process. [18]
G-bands of human chromosome 21 in resolution 850 bphs [3]
Chr.Arm [19] Band [20] ISCN
start [21]
ISCN
stop [21]
Basepair
start
Basepair
stop
Stain [22] Density
21p13031113,100,000gvar
21p123116833,100,0017,000,000stalk
21p11.268310567,000,00110,900,000gvar
21p11.11056127410,900,00112,000,000acen
21q11.11274136712,000,00113,000,000acen
21q11.21367158413,000,00115,000,000gneg
21q21.11584201915,000,00122,600,000gpos100
21q21.22019214422,600,00125,500,000gneg
21q21.32144233025,500,00130,200,000gpos75
21q22.112330248530,200,00134,400,000gneg
21q22.122485261034,400,00136,400,000gpos50
21q22.132610270336,400,00138,300,000gneg
21q22.22703285838,300,00141,200,000gpos50
21q22.32858320041,200,00146,709,983gneg

References

  1. 1 2 "Search results - 21[CHR] AND "Homo sapiens"[Organism] AND ("has ccds"[Properties] AND alive[prop]) - Gene". NCBI. CCDS Release 24 for Homo sapiens. 2022-10-26. Retrieved 2025-01-15.
  2. Tom Strachan; Andrew Read (2 April 2010). Human Molecular Genetics. Garland Science. p. 45. ISBN   978-1-136-84407-2.
  3. 1 2 3 Genome Decoration Page, NCBI. Ideogram data for Homo sapience (850 bphs, Assembly GRCh38.p3). Last update 2014-06-03. Retrieved 2017-04-26.
  4. "Chromosome 21".
  5. Hattori, M.; Fujiyama, A.; Taylor, T. D.; Watanabe, H.; Yada, T.; Park, H.-S.; Toyoda, A.; Ishii, K.; Totoki, Y.; Choi, D.-K.; Soeda, E.; Ohki, M.; Takagi, T.; Sakaki, Y.; Taudien, S.; Blechschmidt, K.; Polley, A.; Menzel, U.; Delabar, J.; Kumpf, K.; Lehmann, R.; Patterson, D.; Reichwald, K.; Rump, A.; Schillhabel, M.; Schudy, A.; Zimmermann, W.; Rosenthal, A.; Kudoh, J.; et al. (2000). "The DNA sequence of human chromosome 21". Nature. 405 (6784): 311–319. Bibcode:2000Natur.405..311H. doi: 10.1038/35012518 . PMID   10830953.
  6. Pertea M, Salzberg SL (2010). "Between a chicken and a grape: estimating the number of human genes". Genome Biol. 11 (5): 206. doi: 10.1186/gb-2010-11-5-206 . PMC   2898077 . PMID   20441615.
  7. "Statistics & download files". HUGO Gene Nomenclature Committee. 2024-04-10. Retrieved 2025-01-15.
  8. "Chromosome 21: Chromosome summary - Homo sapiens". Ensembl Release 112. 2024-05-13. Retrieved 2025-01-15.
  9. "Human chromosome 21: entries, gene names and cross-references to MIM". UniProt. 2024-11-27. Retrieved 2025-01-15.
  10. "Search results - 21[CHR] AND "Homo sapiens"[Organism] AND ("genetype protein coding"[Properties] AND alive[prop]) - Gene". NCBI. 2025-01-19. Retrieved 2025-01-19.
  11. "Search results - 21[CHR] AND "Homo sapiens"[Organism] AND ( ("genetype miscrna"[Properties] OR "genetype ncrna"[Properties] OR "genetype rrna"[Properties] OR "genetype trna"[Properties] OR "genetype scrna"[Properties] OR "genetype snrna"[Properties] OR "genetype snorna"[Properties]) NOT "genetype protein coding"[Properties] AND alive[prop]) - Gene". NCBI. 2025-01-19. Retrieved 2025-01-19.
  12. "Search results - 21[CHR] AND "Homo sapiens"[Organism] AND ("genetype pseudo"[Properties] AND alive[prop]) - Gene". NCBI. 2025-01-19. Retrieved 2025-01-19.
  13. 1 2 3 Sleegers K, Brouwers N, Gijselinck I, Theuns J, Goossens D, Wauters J, Del-Favero J, Cruts M, van Duijn CM, Van Broeckhoven C (2006). "APP duplication is sufficient to cause early onset Alzheimer's dementia with cerebral amyloid angiopathy". Brain. 129 (Pt 11): 2977–83. doi: 10.1093/brain/awl203 . PMID   16921174.
  14. Kohno, T.; Kawanishi, M.; Matsuda, S.; Ichikawa, H.; Takada, M.; Ohki, M.; Yamamoto, T.; Yokota, J. (March 1998). "Homozygous deletion and frequent allelic loss of the 21q11.1-q21.1 region including the ANA gene in human lung carcinoma". Genes, Chromosomes & Cancer. 21 (3): 236–243. doi:10.1002/(sici)1098-2264(199803)21:3<236::aid-gcc8>3.0.co;2-0. ISSN   1045-2257. PMID   9523199. S2CID   24082301.
  15. Genome Decoration Page, NCBI. Ideogram data for Homo sapience (400 bphs, Assembly GRCh38.p3). Last update 2014-03-04. Retrieved 2017-04-26.
  16. Genome Decoration Page, NCBI. Ideogram data for Homo sapience (550 bphs, Assembly GRCh38.p3). Last update 2015-08-11. Retrieved 2017-04-26.
  17. International Standing Committee on Human Cytogenetic Nomenclature (2013). ISCN 2013: An International System for Human Cytogenetic Nomenclature (2013). Karger Medical and Scientific Publishers. ISBN   978-3-318-02253-7.
  18. Sethakulvichai, W.; Manitpornsut, S.; Wiboonrat, M.; Lilakiatsakun, W.; Assawamakin, A.; Tongsima, S. (2012). "Estimation of band level resolutions of human chromosome images". 2012 Ninth International Conference on Computer Science and Software Engineering (JCSSE). pp. 276–282. doi:10.1109/JCSSE.2012.6261965. ISBN   978-1-4673-1921-8. S2CID   16666470.
  19. "p": Short arm; "q": Long arm.
  20. For cytogenetic banding nomenclature, see article locus.
  21. 1 2 These values (ISCN start/stop) are based on the length of bands/ideograms from the ISCN book, An International System for Human Cytogenetic Nomenclature (2013). Arbitrary unit.
  22. gpos: Region which is positively stained by G banding, generally AT-rich and gene poor; gneg: Region which is negatively stained by G banding, generally CG-rich and gene rich; acen Centromere. var: Variable region; stalk: Stalk.